CODEWITHSUNDEEP
bashshellscriptingheredoc
Kam
Kam

Reputation: 6008

How to safely run arbitrary code on a remote machine?

I would like to receive a shell command from a user, and run it as a Linux user with no real privileges.

Today I'm doing this: sudo -u {username} 'sh' '-c' $'{user_command}'

Is this safe?

Upvotes: 1

Views: 298

Answers (1)

hek2mgl
hek2mgl

Reputation: 158020

Manually escaping the ' sounds fragile. I would put the command into a file and execute that file as a script. This avoids command injection by design.

Further note that even an unprivileged account will have read access to many files on the host system, like /etc/passwd or information from /proc. If they would run ps for example, they could see commands from other users.

Therefore I would recommend to run the command in a container. Install docker and run:

# let's say you stored the command in "user.sh" ...
docker run -v "${PWD}:/scripts" -it image_name bash /scripts/user.sh

Another thing which is relevant for security is that people could try to (a) DOS the host machine or (b) DOS other machines or attack them in a different way. For (a), make sure you put pretty strict resource constraints on the docker machine (mem, cpu, number of procs, etc...). For (b), disallow network access for the container.

Upvotes: 1

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